Restrictor plates

[CamaroSS00]

My buddy and i were talking about exaust and intakes and it came abotu thata i remembered soemhting while watchin nascar they were talking about restrictor plates but we couldn't exactly figure out what there for. can anyone help me out and tell me what they do, and if there any good for cars like camaro's?

[Injuneer]

They are a "restriction" required under the NASCAR rules, and purposely installed under the carburetor to limit HP. In theory, by specifying the open area of the restrictor, they can put all teams on the same footing.

Defiinitely not something you would intentionally install on a street car. It would hurt performance, not help it.

[BAS]

This prevents cars from running very dangerously fast at Talledega and some
other track that is very fast.

But this causes drivers to ride very close
together, causing more accidents.

Originally posted by Injuneer
They are a "restriction" required under the NASCAR rules, and purposely installed under the carburetor to limit HP. In theory, by specifying the open area of the restrictor, they can put all teams on the same footing.

Defiinitely not something you would intentionally install on a street car. It would hurt performance, not help it.

[wolfdogs]

i put a restrictor plate on my x wife..........

it worked......



yes..its not for performance....thats for sure.

[94 formula]

While on the subject of Nascar how do they get 800+ hp out of a 350 while the most thats been gotten on a factory car is 405 hp (Z06)? I know there are things like race gas, no emissions contorls, and alot of money and time put in every engine but 400 hp difference is alot out of a same cubic inch engine. Also how is it possible to run at 8,000 rpm with a push rod engine for so long. Any of our cars would probably blow up running at that for even a short time.

[Injuneer]

10,000rpm. And tuned, using inlet runner and exhaust tuning that helps them make huge power in a very narrow RPM range. Huge heads allow huge air flow, and don't have to ALSO meet "streetability" requirements.

Multiply the rpm X minutes in the race, and you will realize that the engine really doesn't have to last very long. The valve springs, for example, carrying huge loads, probably wouldn't last at all in a 10,000mile street car. With a relatively inexpensive valve train, my 381 w/solid roller will run at 7,500rpm all day. They can use high $$$, exotic materials for valve train weight reduction and raise the rpm limit much higher.

It's like a top fuel dragster.... the engine performs at top HP for only 750 revolutions, then gets rebuilt.

[Al 96 Ram Air T/A]

And to add...

If you really think about it, our LT1/LS1 engines are not very efficient. At 5.7 liters, these engines make about 50 hp per liter. Not very efficient. For comparison sake, my Ponitac Vibe Yamaha motor puts out 100 hp per liter, NA. That being the case, if it were as large as my T/A's motor, I would be at 570 hp instead of 325.

So, when looking at NASCAR engines, realize that they are more efficient than street motors, but at a high cost to longevity. Even so, approxiamtely 140 hp per liter is nothing great. Especially not when you consider a Top Fuel dragster is close to 1000 hp per liter. Granted it's with a power adder, but these engines are exponentially more efficient than a NASCAR engine, but again, at a cost. They are designed to last 4 - 5 seconds before needing a rebuild. Call me crazy, but I prefer my 50 hp per liter motor which is good for at least 100,000 miles before needing work.

[94 formula]

I never looked at it that way. You still gotta admit though there an amazing piece of machinery.

[PG45]

It is not as much the parts but more the tuning that goes into a winston cup motor. And another thing is that granted the parts are relatively expensive, its the R&D and time of tunning that brings up the price. A busch engine and winston cup engine are basically the same parts but you get about 800 from the wc and 550-600 from the busch. That difference is from the engine builder and how it is tuned. I know i guy that tried to build his own "winston cup" engine for his car. Spent like $35000 in parts to build it and get it balanced and all the other trimmings to only get like 600 hp at like 8500. Why, all in the tuning. The only part that he cant get his hands on is a cam (his biggest problem). Those cams are all grinded buy the engine builders to meet the requirements of the track. Not to keep rambling, but they dont get 800 at all the tracks. At some tracks they will have anywhere from 50 to 100 less. And at daytona and talladega with the restictor plates, they are pushin 500 maybe.

Phew im done!

[nathanaf8388]

"that goes into a winston cup motor. And another thing is that granted the parts" not to be a $marta$$ but its not winston cup anymore its.... ummm.... some cellpohne company cant forget the name but yeha they changed the name

[Craig 94 TA GT]

OK, I know some estimated figures off the top of my head. Dale Jarrett, 1 1/2 years ago at Michigan dynoed his car after the race and got 738 RWHP. A few others were in that range, Dodge being the lowest at ~720 RWHP. Now with the restrictor plates, they are making ~385 RWHP 2 years ago.
Now, I'm sure they are dynoing at 750+ RWHP, but NASCAR continues to restrict the superspeedway horsepower to the same amount. As mentioned earlier, the weight of each engine part is mandated, to try to keep the revs and horsepower down a bit.
As far as Busch vs Winston Cup motors, Busch are now making 700-720 hp, and WC is around 800-850. The reason Busch is that close is because they are allowed to use roller lifters and cam (unlike WC), but are still restricted to a 390 carb, compared to 780 for WC.
True, the power bandwidth of a Winston cup motor is not streetable, however, I have seen a dyno chart of a Hendrick motor (one of the underperforming ones: 768 hp @ 8000). He was selling it for $40,000 on his web site and gave a dyno chart: at 5000 RPM, it made well over 600 hp, and at 6000 RPM, it was close to 700 hp. Above that, the numbers just grew rapidly. So it's still making a substantial amount of horsepower at a somewhat wide RPM range.
Sorry for getting a little off track...it's been a looooong day for me.

[Joe 1320]

The whole reason for restrictor plates in the first place is Nascar felt that the speeds were climbing to an unsafe level. Engine technology was climbing at an alarming rate and the saftey of the drivers and spectators was becomming an issue. As HP level keep increasing, restrictor plates change to compensate. A while back there was a top speed shootout among various racing sanctions. Up to the next to the last entry, the Porsche protoype was in the top spot with something like a 226 mph speed and the factory team was pretty cocky. A Nascar Grand National car removed it's restrictor plate, taped up a few body gaps and literally blew the competition off the track and went 248. That was perhaps 8 years ago. Imagine what the speed could be today.

[Craig 94 TA GT]

Wow, do you have any more info on what the other racing series' got? That is pretty cool. I heard Benny Parsons talking about it during a race this year, but didn't get specific. I'm guessing 260+would be done nowadays.

Regarding my earlier post, I apologize because I have off about 1000 RPM. At 6000, it made 600+ hp. The engine generated 536 ft/lb of torque, and the hp and tq always meet at 5250, thus it was 500+ hp at 5000 RPM.